Apparatus and method for sharing a network I/O adapter between logical partitions

ABSTRACT

An I/O adapter sharing mechanism in a logically partitioned computer system allows sharing a network I/O adapter between logical partitions in an efficient manner. A first logical partition owns (or controls) the I/O adapter, and a second logical partition desires to use (or share) the I/O adapter. An I/O adapter device driver that includes a hardware interface is provided in the first logical partition. A virtual device driver is provided in the second logical partition that provides a set of functions that is at least partially defined by querying the I/O adapter device driver in the first logical partition. The I/O adapter sharing mechanism includes a transfer mechanism that allows data to be transferred directly from the virtual device driver in the second logical partition to the I/O adapter without passing through the I/O adapter device driver in the first logical partition.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention generally relates to data processing, and morespecifically relates to the sharing of resources between logicalpartitions in a logically partitioned computer system.

2. Background Art

Since the dawn of the computer age, computer systems have evolved intoextremely sophisticated devices that may be found in many differentsettings. Computer systems typically include a combination of hardware(e.g., semiconductors, circuit boards, etc.) and software (e.g.,computer programs). As advances in semiconductor processing and computerarchitecture push the performance of the computer hardware higher, moresophisticated computer software has evolved to take advantage of thehigher performance of the hardware, resulting in computer systems todaythat are much more powerful than just a few years ago.

The combination of hardware and software on a particular computer systemdefines a computing environment. Different hardware platforms anddifferent operating systems thus provide different computingenvironments. In recent years, engineers have recognized that it ispossible to provide different computing environments on the samephysical computer system by logically partitioning the computer systemresources to different computing environments. The iSeries computersystem developed by IBM is an example of a computer system that supportslogical partitioning. If logical partitioning on an iSeries computersystem is desired, partition manager code (referred to as a “hypervisor”in iSeries terminology) is installed that allows defining differentcomputing environments on the same platform. Once the partition manageris installed, logical partitions may be created that define differentcomputing environments. The partition manager manages the logicalpartitions to assure that they can share needed resources in thecomputer system while maintaining the separate computing environmentsdefined by the logical partitions.

A computer system that includes multiple logical partitions typicallyshares resources between the logical partitions. For example, a computersystem with a single CPU could have two logical partitions defined, with50% of the CPU allocated to each logical partition, with 33% of thememory allocated to the first logical partition and 67% of the memoryallocated to the second logical partition, and with two different I/Oslots allocated to the two logical partitions, one per partition. Oncelogical partitions are defined and shared resources are allocated to thelogical partitions, each logical partition acts as a separate computersystem. Thus, in the example above that has a single computer systemwith two logical partitions, the two logical partitions will appear forall practical purposes to be two separate and distinct computer systems.

Logical partitions typically communicate using an internal virtual localarea network (VLAN). This VLAN implementation simplifies the migrationof multiple computer systems into a single computer system with multiplelogical partitions. Where the separate computer systems used tocommunicate over LAN connections, the logical partitions may nowcommunicate in similar manner over their VLAN connections.

When logical partitions share a resource, such as an I/O adapter, one ofthe logical partitions is typically designated as the “owner” of theresource, and other logical partitions may share the resource bycommunicating with the logical partition that owns the resource. For thediscussion herein, the term “hosting partition” refers to a logicalpartition that owns a resource, and the term “hosted partition” refersto a logical partition that does not own the resource but that desiresto use (or share) the resource by communicating with the hostingpartition. When an application in a hosted partition needs tocommunicate with a shared network I/O adapter in the hosting partition(for example, an Ethernet adapter), the application typically passes amessage to its TCP stack, which passes the message to its IP stack,which then communicates the message to the VLAN device driver. Thepartition manager monitors data buffers in memory that correspond to theVLAN device driver, and when transmit data is present, the partitionmanager copies the data in the data buffers from hosted partition memoryto hosting partition memory. The VLAN device driver on the hostingpartition then reads the copied data, and sends the data to an IPforwarding mechanism in the hosting partition. The IP forwardingmechanism then sends the data to the I/O adapter device driver, whichcommunicates the data to its hardware interface. The partition managerthen manages the transfer of data from the hardware interface to the I/Oadapter, resulting in the data being transmitted to the networkconnection coupled to the I/O adapter. While this implementation for I/Oadapter sharing is very easy to implement, it suffers from seriousperformance issues, especially as the number of logical partitionssharing the resource increases. Without a way to share an I/O adapterbetween logical partitions in a more efficient manner, the computerindustry will continue to suffer from performance penalties that resultfrom sharing an I/O adapter in a logically partitioned computer system.

DISCLOSURE OF INVENTION

An I/O adapter sharing mechanism in a logically partitioned computersystem allows sharing a network I/O adapter between logical partitionsin an efficient manner. A first logical partition owns (or controls) theI/O adapter, and a second logical partition desires to use (or share)the I/O adapter. An I/O adapter device driver that includes a hardwareinterface is provided in the first logical partition. A virtual devicedriver is provided in the second logical partition that provides a setof functions that is at least partially defined by querying the I/Oadapter device driver in the first logical partition. The I/O adaptersharing mechanism includes a transfer mechanism that allows data to betransferred directly from the virtual device driver in the secondlogical partition to the I/O adapter without passing through the I/Oadapter device driver in the first logical partition.

The foregoing and other features and advantages of the invention will beapparent from the following more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

BRIEF DESCRIPTION OF DRAWINGS

The preferred embodiments of the present invention will hereinafter bedescribed in conjunction with the appended drawings, where likedesignations denote like elements, and:

FIG. 1 is a block diagram of a computer apparatus that supports logicalpartitioning and I/O adapter sharing in accordance with the preferredembodiments;

FIG. 2 is a flow diagram of a prior art method for configuring logicalpartitions to share an I/O adapter;

FIG. 3 is a block diagram showing portions of a prior art logicallypartitioned computer system that shares an I/O adapter between logicalpartitions;

FIG. 4 is a flow diagram of a prior art method for sharing the I/Oadapter in the computer system shown in FIG. 3;

FIG. 5 is a block diagram showing portions of the computer system inFIG. 1 that shares an I/O adapter between logical partitions inaccordance with the preferred embodiments;

FIG. 6 is a flow diagram of a method in accordance with the preferredembodiments for configuring logical partitions to share an I/O adapter;and

FIG. 7 is a flow diagram of a method in accordance with the preferredembodiments for sharing the I/O adapter in the computer system shown inFIG. 5.

BEST MODE FOR CARRYING OUT THE INVENTION

According to preferred embodiments of the present invention, an I/Oadapter sharing mechanism efficiently shares a network I/O adapterbetween logical partitions. An I/O adapter device driver is provided ina first logical partition that owns or controls the I/O adapter. Avirtual device driver is provided in a second logical partition thatneeds to use (share) the I/O adapter. The virtual device driver includesa set of functions that are at least partially determined by queryingthe I/O adapter device driver in the first logical partition. In thismanner, the virtual device driver can support any advanced hardwarefunctions that the I/O adapter is capable of performing. In addition,the I/O adapter sharing mechanism uses a transfer mechanism to transferdata between the virtual device driver in the second logical partitionand the I/O adapter without passing through the I/O adapter devicedriver in the first logical partition.

Referring to FIG. 1, a computer system 100 is an enhanced IBM eServeriSeries computer system, and represents one suitable type of computersystem that supports logical partitioning and I/O adapter sharing inaccordance with the preferred embodiments. Those skilled in the art willappreciate that the mechanisms and apparatus of the present inventionapply equally to any computer system that supports logical partitions.As shown in FIG. 1, computer system 100 comprises one or more processors110 connected to a main memory 120, a mass storage interface 130, adisplay interface 140, a network interface 150, and a plurality of I/Oslots 180. Note that one or more of mass storage interface 130, displayinterface 140, and network interface 150 could be embedded I/O oncomputer system 100. These system components are interconnected throughthe use of a system bus 160. Mass storage interface 130 is used toconnect mass storage devices (such as a direct access storage device155) to computer system 100. One specific type of direct access storagedevice is a CD RW drive, which may read data from a CD RW 195. Note thatmass storage interface 130, display interface 140, and network interface150 may actually be implemented in adapters coupled to I/O slots 180. AnI/O adapter is one suitable network interface 150 that may beimplemented in an external card that is plugged into one of the I/Oslots 180.

Main memory 120 contains a partition manager 121 and N logicalpartitions 125, shown in FIG. 1 as logical partitions 125A through 125N.Partition manager 121 preferably creates these N logical partitions 125.Each logical partition 125 preferably includes a corresponding operatingsystem 126, shown in FIG. 1 as operating systems 126A through 126N.

Partition manager 121 includes an I/O adapter sharing mechanism 122 thatefficiently shares an I/O adapter between logical partitions. While theI/O adapter sharing mechanism 122 is shown in FIG. 1 to reside in mainmemory 120, one skilled in the art will appreciate that I/O adaptersharing mechanism preferably includes different pieces that residewithin the logical partitions 125 and within the partition manager 121,and that sharing of an I/O adapter of the preferred embodiments occursthrough cooperation of these different pieces, as shown in FIGS. 5-7,which are discussed in more detail below.

Operating system 126 is a multitasking operating system, such as OS/400,AIX, or Linux; however, those skilled in the art will appreciate thatthe spirit and scope of the present invention is not limited to any oneoperating system. Any suitable operating system can be used. Operatingsystem 126 is a sophisticated program that contains low-level code tomanage the resources of computer system 100. Some of these resources areprocessor 110, main memory 120, mass storage interface 130, displayinterface 140, network interface 150, system bus 160, and I/O slots 180.The operating system 126 in each partition may be the same as theoperating system in other partitions, or may be a completely differentoperating system. Thus, one partition can run the OS/400 operatingsystem, while a different partition can run another instance of OS/400,possibly a different release, or with different environment settings(e.g., time zone or language). The operating systems in the logicalpartitions could even be different than OS/400, provided it iscompatible with the hardware (such as AIX or Linux). In this manner thelogical partitions can provide completely different computingenvironments on the same physical computer system.

The partitions 125A-125N are shown in FIG. 1 to reside within the mainmemory 120. However, one skilled in the art will recognize that apartition is a logical construct that includes resources other thanmemory. A logical partition typically specifies a portion of memory,along with an assignment of processor capacity and other systemresources, such as I/O slots 180 (and I/O adapters, which may reside inI/O slots 180). Thus, one partition could be defined to include twoprocessors and a portion of memory 120, along with one or more embeddedI/O that can provide the functions of mass storage interface 130,display interface 140, network interface 150, or interfaces to I/Oadapters or other devices plugged into I/O slots 180. Another partitioncould then be defined to include three other processors, a differentportion of memory 120, one or more embedded I/O, and I/O slots 180. Thepartitions are shown in FIG. 1 to symbolically represent logicalpartitions, which would include system resources outside of memory 120within computer system 100. Note also that the partition manager 121preferably resides in memory and hardware separate from the logicalpartitions and includes facilities and mechanisms that are not directlyavailable to the logical partitions.

Computer system 100 utilizes well known virtual addressing mechanismsthat allow the programs of computer system 100 to behave as if they onlyhave access to a large, single storage entity instead of access tomultiple, smaller storage entities such as main memory 120 and DASDdevice 155. Therefore, while partition manager 121 and the partitions125A-125N are shown to reside in main memory 120, those skilled in theart will recognize that these items are not necessarily all completelycontained in main memory 120 at the same time. It should also be notedthat the term “memory” is used herein to generically refer to the entirevirtual memory of computer system 100.

Processor 110 may be constructed from one or more microprocessors and/orintegrated circuits. Processor 110 executes program instructions storedin main memory 120. Main memory 120 stores programs and data thatprocessor 110 may access. When computer system 100 starts up, processor110 initially executes the program instructions that make up thepartition manager 121, which initializes the operating systems in thelogical partitions.

Although computer system 100 is shown to contain only a single systembus, those skilled in the art will appreciate that the present inventionmay be practiced using a computer system that has multiple buses. Inaddition, the I/O interfaces that are used in the preferred embodimenteach may include separate, fully programmed microprocessors that areused to off-load compute-intensive processing from processor 110, as iniSeries input/output processors, or may be simple industry standard I/Oadapters (IOAs).

Display interface 140 is used to directly connect one or more displays165 to computer system 100. These displays 165, which may benon-intelligent (i.e., dumb) terminals or fully programmableworkstations, are used to allow system administrators and users tocommunicate with computer system 100. Note, however, that while displayinterface 140 is provided to support communication with one or moredisplays 165, computer system 100 does not necessarily require a display165, because all needed interaction with users and other processes mayoccur via network interface 150.

Network interface 150 is used to connect other computer systems and/orworkstations (e.g., 175 in FIG. 1) to computer system 100 across anetwork 170. The present invention applies equally no matter howcomputer system 100 may be connected to other computer systems and/orworkstations, regardless of whether the network connection 170 is madeusing present-day analog and/or digital techniques or via somenetworking mechanism of the future. In addition, many different networkprotocols can be used to implement a network. These protocols arespecialized computer programs that allow computers to communicate acrossnetwork 170. TCP/IP (Transmission Control Protocol/Internet Protocol) isan example of a suitable network protocol.

At this point, it is important to note that while the present inventionhas been and will continue to be described in the context of a fullyfunctional computer system, those skilled in the art will appreciatethat the present invention is capable of being distributed as a programproduct in a variety of forms, and that the present invention appliesequally regardless of the particular type of computer readable signalbearing media used to actually carry out the distribution. Examples ofsuitable signal bearing media include: recordable type media such asfloppy disks and CD RW (e.g., 195 of FIG. 1), and transmission typemedia such as digital and analog communications links.

A detailed discussion of prior art I/O network adapter sharing is nowpresented, which provides a context for discussing the I/O adaptersharing in accordance with the preferred embodiments. Referring to FIG.2, a method 200 represents steps that are taken in the prior art toprepare two logical partitions to share an I/O adapter. The I/O adapteris assigned to a logical partition (step 210), which is called a“hosting partition” because it is the owner (or host) of the I/Oadapter. Internal VLAN communication is then set up between the hostingpartition and any partition (hosted partition) that wants to use (share)the I/O adapter in the hosting partition (step 220). IP forwarding isthen setup in the hosting partition (step 230). Note that the individualsteps in method 200 may be performed at any time before the logicalpartitions may share the I/O adapter at run-time, including when thelogical partitions are created and defined, when the logical partitionsare first brought up and executed, or at run-time. In the most preferredimplementation, the I/O adapter is assigned to the hosting partition instep 210 during partition configuration, the VLAN communication setup instep 220 is performed when the logical partitions are loaded and arepreparing to be run, and the IP forwarding setup in step 230 isperformed after the logical partitions are running.

A block diagram of certain logical elements in a prior art logicallypartitioned computer system 300 is shown in FIG. 3. The hostingpartition 302A and hosted partition 302B are controlled by a partitionmanager 321. The hosted partition 302B includes one or more applications310, a TCP mechanism 320, an IP mechanism 330, and a virtual LAN (VLAN)device driver 340. The hosting partition 302A includes a VLAN devicedriver 350, an IP forwarding mechanism 360, and an I/O adapter devicedriver 370 that includes a hardware interface 380. Note that hostingpartition 302A would normally include a TCP layer that is not shownbecause the TCP layer in the hosting partition 302A is not used totransmit data to a shared I/O adapter. The hosting partition 302A andhosted partition 302B communicate via the partition manager 321 andVLAN. Note also that the partition manager 321 manages the transfer ofdata between the hardware interface 380 and the I/O adapter 390.

We see from correlating FIGS. 2 and 3 that step 220 in FIG. 2 installsthe VLAN device driver 340 in the hosted partition 302B, installs theVLAN device driver 350 in the hosting partition 302A, and enables VLANcommunications within the partition manager 321. Step 230 in FIG. 2installs and enables the IP forwarding mechanism 360 in the hostingpartition 302A so that data received by VLAN device driver 350 that isintended for the I/O adapter 390 is forwarded to the I/O adapter devicedriver 370.

Referring to FIG. 4, a prior art method 400 shows the steps for thehosted partition 302B in FIG. 3 to share the I/O adapter 390. Method 400represents the steps that are performed at run-time when data needs tobe transferred between an application 310 in the hosted partition 302Band the I/O adapter 390. Note that the steps in method 400 are bestunderstood by also referring to FIG. 3. First, the application 310 inthe hosted partition 302B writes transmit data for the I/O adapter 390to its TCP mechanism 320 (step 410). The TCP mechanism 320 formats thedata into frames, adds a TCP checksum, and writes the data to the IPmechanism 330 (step 420). The IP mechanism 330 then adds an IP checksum,and writes the data to the VLAN device driver 340 (step 430). Thepartition manager then copies the data between memory in the hostedpartition 302B and memory in hosting partition 302A (step 440). The VLANdevice driver 350 in the hosting partition 302A then reads the data,determines the data needs to be processed by the IP layer, and in thiscase by the IP forwarding mechanism 360 (step 450). The IP forwardingmechanism then forwards the data to the I/O adapter device driver 370,which writes the data to its hardware interface 380 (step 460). Thepartition manager 321 then manages the direct memory access (DMA) of thetransmit data by the I/O adapter 390 from memory in the hostingpartition 302A to the I/O adapter 390 (step 470). The I/O adapter thentransmits the data (step 480). For the sake of simplicity, method 400relates to the transfer of data from an application 310 in the hostedpartition 302B to the I/O adapter 390 for transmission. One skilled inthe art will appreciate that transfers from the I/O adapter 390 to theapplication 310 occur in similar fashion in a reverse order.

There are several problems with the prior art method for sharing an I/Oadapter between logical partitions shown in FIGS. 2-4. First, the datapath shown as the dotted line between the application 310 and the I/Oadapter 390 follows the same path as the control message path, shown asthe solid line. As a result, all data to be communicated betweenapplication 310 and I/O adapter 390 has to go through three devicedrivers (VLAN in hosted partition, VLAN in hosting partition and I/Oadapter) instead of going through a single device driver (I/O adapter)when the I/O adapter is dedicated. In addition, data is copied betweenVLAN device drivers by the partition manager, resulting in an extra datacopy. The prior art method also requires two IP levels, increasingoverhead. The result is that shared I/O adapters in the prior art haveperformance levels that are significantly lower than for dedicated I/Oadapters.

Another significant disadvantage is that the hosted partition cannottake advantage of any hardware enhancements present on the I/O adapter,because an application that uses TCP/IP and VLAN device driver 340 hasno knowledge of the capabilities of the I/O adapter 390. Most currentEthernet adapters support TCP and IP “checksum offload.” This means thatthe I/O adapter 390 itself may be configured to generate the checksumsfor the TCP and IP messages, thereby relieving the software of theoverhead of generating checksums at the TCP and IP layers. When an I/Oadapter that supports checksum offload is used in a dedicated manner,the I/O adapter can be configured to generate the checksums for TCP andIP messages, which can improve performance of the system because no CPUcycles are required to generate the checksums. However, when the sameI/O adapter that supports checksum offload is used in a shared manner asshown in FIG. 3, the hosted TCP and IP layers have no way of knowingthat the I/O adapter 390 has this capability. As a result, this checksumoffload capability cannot be used by any hosted partitions. Note thatthis capability may be used by the hosting partition, but not by any ofthe hosted partitions.

Another advanced adapter function provided by some 1 gigabit-per-second(Gbps) Ethernet adapters is known as “large frame send.” With thisfeature enabled, the I/O adapter may process transmit frames that are aslarge as 64 Kbytes. The adapter splits a 64 Kbyte frame into 1,500 byteframes, including the appropriate TCP and IP headers. In the prior art,1,500 byte frames are normally used. It is evident that the sending of64 Kbyte frames is more efficient than the sending of an equivalentnumber of 1,500 byte frames, because each frame requires checksumprocessing. In the prior art, more context switching occurs betweenhosted and hosting partitions for 1,500 byte frames than if 64 Kbyteframes could be used. The large frame send capability of some I/Oadapters could significantly enhance performance, but this capabilitywill go unused in all hosted partitions. Again, because the hostedpartitions have no way to determine the capability of the I/O adapter,they must assume that no advanced functions are present.

Yet another advanced adapter function supported on some known Ethernetadapters is known as “IPsec”, which is an encryption standard for TCP/IPand UDP sessions. Like the other advanced adapter functions, thisfunction is unavailable to hosted partitions. Still another advancedadapter function that is planned for future Ethernet adapters is knownas TCP/IP Offload Engine, or TOE. This allows TCP and IP processing tobe done directly on the adapter, relieving the computer system from theCPU cycles that are normally required to perform TCP and IP processing.Again, this advanced adapter function is unavailable to hostedpartitions using the prior art method for sharing an I/O adapter betweenlogical partitions.

Another disadvantage of the prior art method for sharing an I/O adapterbetween logical partitions is that IP forwarding configuration iscomplex and error-prone. The hosting partition must have IP forwardingturned on and configured properly in order to share the I/O adapter. Allof these disadvantages in the prior art method for sharing an I/Oadapter are not present in the method of the preferred embodiments,which is discussed in detail below.

While FIG. 1 shows a sample computer system that includes some of thesalient features of both hardware and software in accordance with thepreferred embodiments, a more detailed logical view of some of thecomponents in FIG. 1 is shown as system 500 in FIG. 5. The VLAN devicedrivers in the prior art are replaced by an I/O hosting interface 550 inthe hosting partition 125A and a virtual hosted device driver 540 in thehosted partition 125B. The I/O hosting interface 550 and virtual hosteddevice driver 540 communicate with each other when data needs to betransferred between the application 310 and the I/O adapter 390. One ofthe significant functions provided by the I/O hosting interface 550 isthe ability for the virtual hosted device driver 540 to query the I/Oadapter hosting device driver 560 to determine what functions aresupported by the I/O adapter 390. The virtual hosted device driver 540thus includes a set of functions that are at least partially determinedby the functions available in the I/O adapter hosting device driver. Onesuitable way to configure the virtual hosted device driver 540 is toquery the I/O adapter hosting device driver 560 for its availablefunctions. Of course, other methods of communicating the availablefunctions of the I/O adapter hosting device driver 560 to the virtualhosted device driver 540 are within the scope of the preferredembodiments. For example, a configuration table or file in the partitionmanager could be written that contains the available functions for theI/O adapter hosting device driver, and this table or file could be readto determine available functions for the virtual hosted device driver.

Because the virtual hosted device driver 540 has a set of functions thatare determined by the available functions of the I/O adapter hostingdevice driver 560, hosting partitions may now take advantage of anyperformance enhancement offered by the I/O adapter, including checksumoffload, large frame send, IPsec, TOE, etc. As a result, the transmitdata for application 310 may take advantage of all the advanced featuresof I/O adapter 390, even though I/O adapter 390 is being shared withhosting partition 125A. Thus, if we assume that I/O adapter 390 supportschecksum offload and large frame send, and that these features areenabled on the I/O adapter 390 and within the virtual hosted devicedriver 540, the TCP mechanism 520 does not have to generate a checksum,and may construct a frame as large as 64 Kbytes instead of 1,500 byteframes. In addition, the IP mechanism 530 does not have to generate achecksum. The advanced features of the I/O adapter 390 may thus be usedby the hosted partitions that share the I/O adapter 390.

Another significant advantage of system 500 in FIG. 5 is that data mayhave a shortened path compared to the path for control messages. Thepath for control messages is shown as a solid line, while the path fordata is shown as a dotted line. When the application 310 needs to senddata to the I/O adapter 390, a message is written by application 310 toTCP mechanism 520, which constructs a frame and sends the frame to IPmechanism 530. The IP mechanism 530 then sends the frame to the virtualhosted device driver 540. A suitable message is then written to the I/Ohosting interface 550. We assume this message includes pointers to alist of buffers within the hosted partition 125B that contain the datato be transmitted. This message is then written by the I/O hostinginterface 550 to the I/O adapter hosting device driver 560, which writesthe message to its hardware interface 380. We assume for this examplethat the message specifies the location in memory in the hostedpartition where the data was written by the virtual hosted device driver540. In response, the partition manager 121 preferably manages thetransfer of data using redirected remote DMA directly from the memory inthe hosted partition that contains the data to the I/O adapter 390,shown by the dotted line. In the prior art, an I/O adapter only has DMAaccess to memory in the logical partition that owns the I/O adapter. Inthe preferred embodiments, however, the partition manager may setupadditional address translation entries and authentication capability toallow the I/O adapter DMA access to memory within the hosted partition125B. Note that the dotted data path shows data being transferred fromthe virtual hosted device driver 540 to the I/O adapter 390. Note,however, that the data need not reside within the virtual hosted devicedriver, but may reside in any portion of memory within the hostedpartition 125B that may be accessed by the virtual hosted device driver540 and that may be accessed by a redirected remote DMA operation. Thismeans that prior art I/O adapters can be used to take advantage of theadvantages of the preferred embodiments without requiring anyenhancements, because the I/O adapter DMA operation from memory in thehosted partition 302B is the same type of operation as a DMA operationfrom memory in the hosting partition 302A.

Referring to FIG. 6, a method 600 in accordance with the preferredembodiments for setting up I/O adapter sharing between logicalpartitions begins by assigning an I/O adapter to a hosting partition(step 210). The I/O hosting interface on the hosting partition is thensetup (step 620). The I/O adapter hosting device driver is then queriedto determine the capabilities of the I/O adapter (step 630). The virtualhosted device driver in the hosted partition is then installed withcapabilities (i.e., a set of functions) that may be, in part, determinedby the query in step 630 (step 640). In this manner the virtual hosteddevice driver may be configured to support any advanced featuresavailable on the I/O adapter, thereby making these advanced featuresavailable to the hosted partitions. At this point method 600 is done,and the logical partitions are ready to be run.

Referring to FIG. 7, a method 700 in accordance with the preferredembodiments shows steps that are preferably performed at run-time toshare the I/O adapter of FIG. 5 that is owned (or controlled) by thehosting partition 125A with the hosted partition 125B. When theapplication 310 in the hosted partition 125B needs to transfer data tothe I/O adapter 390, it starts by writing the transmit data to the TCPmechanism 520 (step 410). The TCP mechanism 520 then writes the data tothe IP mechanism 530 (step 720). The IP mechanism 530 the writes thedata to the virtual hosted device driver 540 (step 730). The virtualhosted device driver 540 then sends a message to the I/O hostinginterface 550 that indicates that data in the hosted partition 125Bneeds to be sent to the I/O adapter (step 740). This message preferablyidentifies a location within the memory of the hosted partition 125Bwhere the data to be transferred is located. The virtual hosted devicedriver 540 and I/O hosting interface 550 are preferably designed tominimize context switching between partitions, thereby enhancing systemperformance. The I/O hosting interface 550 passes the message to the I/Oadapter hosting device driver 560, which passes the message to itshardware interface 380 (step 750). The partition manager then reads themessage from the hardware interface 380 and manages the direct DMA ofthe data from the hosted partition 125B to the I/O adapter 390 (step760). The I/O adapter 390 then transmits the data 780 to the networkconnection to which it is connected (step 770).

Method 700 assumes data needs to be transferred from the application 310to the I/O adapter 390 in FIG. 5. Method 700 results in significantperformance enhancement in transmitting data to I/O adapter 390. In thecase of the I/O adapter receiving data that needs to be written to thehosted partition, the performance enhancement is not as significant. Weassume there are data receive buffers in memory in the hosting partition125A. When data is received by the I/O adapter, it is written to thedata buffers in the hosting partition. An interrupt then occurs, whichnotifies the I/O adapter hosting device driver 560 that data has beenreceived. The data is passed to the I/O hosting interface 550, whichuses the partition manager 121 to pass the data to the virtual hosteddevice driver 540 in the appropriate logical partition. The virtualhosted device driver then passes the data to the IP mechanism 530, thento the TCP mechanism 520, and finally to the application 310. Becausethe improvement in receiving data by the shared I/O adapter 390 is notnearly as significant as the improvement in transmitting data, thereceive case is not discussed further. Note, however, that computersystem servers typically transmit substantially more data than theyreceive.

The preferred embodiments provide a significant advance over the priorart by providing virtual device drivers in each hosted partition thatmay reflect advanced functions provided by the I/O adapter. As a result,advanced functions such as checksum offload, large frame send, IPsec,and TOE may be used by hosted partitions, significantly enhancing theperformance of communications with the I/O adapter for these hostedpartitions. These virtual device drivers are much smaller and simplerthan a device driver for a physical I/O adapter, because virtual devicedrivers do not require a hardware interface, do not require low-leveladapter management, and do not require extensive error recoveryfunctions. In addition, the message protocol between the virtual hosteddevice driver and the I/O hosting mechanism allows identifying transmitdata within the hosted logical partition that may be directlytransferred to the I/O adapter without passing through the I/O adapterhosting device driver. The result is a significant improvement in systemperformance when sharing an I/O adapter between logical partitions.

One skilled in the art will appreciate that many variations are possiblewithin the scope of the present invention. Thus, while the invention hasbeen particularly shown and described with reference to preferredembodiments thereof, it will be understood by those skilled in the artthat these and other changes in form and details may be made thereinwithout departing from the spirit and scope of the invention.

1. A computer-implemented method for sharing a shared network I/Oadapter between first and second logical partitions on a computerapparatus, the method comprising the steps of: (A) providing an I/Oadapter device driver in the first logical partition, the I/O adapterdevice driver including a hardware interface to the shared network I/Oadapter; (B) determining a plurality of functions provided by the sharednetwork I/O adapter by querying the I/O adapter device driver for itsavailable functions; (C) providing a virtual device driver in the secondlogical partition, the virtual device driver providing a set offunctions at least partially determined by the plurality of functionsdetermined in step (B); and (D) a partition manager that communicatesbetween the first and second logical partitions controlling exchange ofinformation between the virtual device driver and the I/O adapter devicedriver.
 2. The method of claim 1 further comprising the step oftransferring data between the virtual device driver and the sharednetwork I/O adapter without the data passing through the I/O adapterdevice driver.
 3. A computer-implemented method for sharing a sharednetwork I/O adapter between first and second logical partitions on acomputer apparatus, the method comprising the steps of: (A) defining thefirst and second logical partitions, the first logical partitioncontrolling the shared network I/O adapter and the second logicalpartition using the shared network I/O adapter controlled by the firstlogical partition, the first logical partition comprising an I/O adapterdevice driver that includes a hardware interface to the shared networkI/O adapter, the second logical partition comprising a virtual devicedriver that receives data to be sent to the shared network I/O adapterand data received from the shared network I/O adapter; (B) determining aplurality of functions provided by the shared network I/O adapter byquerying the I/O adapter device driver for its available functions; (C)providing a set of functions for the virtual device driver that is atleast partially determined by the plurality of functions determined instep (B); and (D) a partition manager that communicates between thefirst and second logical partitions communicating between the virtualdevice driver and the I/O adapter device driver.
 4. The method of claim3 further comprising the step of transferring data between the virtualdevice driver and the network I/O adapter without the data passingthrough the I/O adapter device driver.
 5. A computer-implemented methodfor sharing a shared network I/O adapter between first and secondlogical partitions on a computer apparatus, the method comprising thesteps of: (A) defining the first and second logical partitions on theapparatus, the first logical partition controlling the shared networkI/O adapter and the second logical partition using the shared networkI/O adapter controlled by the first logical partition; (B) providing anI/O adapter device driver in the first logical partition, the I/Oadapter device driver including a hardware interface to the sharednetwork I/O adapter; (C) providing a virtual device driver in the secondlogical partition, the virtual device driver providing a set offunctions at least partially determined from querying the I/O adapterdevice driver in the first logical partition for its availablefunctions; and (D) a partition manager that communicates between thefirst and second logical partitions communicating between the virtualdevice driver in the second logical partition and the I/O adapter devicedriver in the first logical partition.
 6. The method of claim 5 furthercomprising the step of transferring data between the virtual devicedriver and the shared network I/O adapter without the data passingthrough the I/O adapter device driver.
 7. A computer-implemented methodfor sharing a shared network I/O adapter between first and secondlogical partitions on a computer apparatus, the method comprising thesteps of: (A) defining the first and second logical partitions on theapparatus, the first logical partition controlling a shared network I/Oadapter and the second logical partition using the shared network I/Oadapter controlled by the first logical partition; (B) providing apartition manager that performs the steps of: (B1) querying an I/Oadapter device driver in the first logical partition for its availablefunctions; (B2) providing a virtual device driver in the second logicalpartition with a set of functions at least partially determined from theavailable functions determined in step (B1); (B3) receiving at least onetransmit message from the virtual device driver in the second logicalpartition; (B4) sending at least one transmit message to the I/O adapterdevice driver in the first logical partition that includes a hardwareinterface to the shared network I/O adapter; and (B5) transferring datafrom the virtual device driver in the second logical partition to theshared network I/O adapter without the data passing through the I/Oadapter device driver in the first logical partition.